Deinking



Patented Mar. 30, 1954 OFFICE DEINKING Jean Ernest Ziindel, Kayserberg,France, and Robert S. Aries, Brooklyn, N. Y.

N Drawing. Application July 20, 1949, Serial No. 105,913

3 Claims. (Cl. 92-'-1.5)

This invention relates to deinking of waste paper and more particularlyto deinking of newsprint.

Many processes and compositions are found in the prior art that have astheir object the recovery of newsprint in re-useable form. In order tobe re-useable the recovered pulp should possess a whiteness equal to orapproaching that of the original unprinted sheet. This desired result isvery difficult to attain with newsprint, because newsprint is generallycomposed of about 75 per cent ground wood pulp and about 25 per centsulfite pulp, i. e. wood pulp obtained by the chemical sulfite processfor dissolving out the lignin constituents. As is commonly known groundwood consists of small slivers of wood rubbed from a pulp wood log bymeans of frictional pressure between the log and a pulp-stone. Theslivers have'jagged sawtooth ends and there by afford excellent crevicesfor trapping the carbon particles of the printers ink used in printingnewsprint. Because of this trapping effect of ground wood for carbonparticles substantially all prior art newsprint recovery processesfailed to produce a re-useable pulp of a high quality of whiteness, butinstead produced a dull greyish sheet.

In order to obtain a high quality white pulp we have found it desirableto attack the problem in a threefold manner, viz. (a) a chemical agentto partially disintegrate the binder and facilitate carbon removal, (b)a mechanical aid whichremoves the pigment by friction and (c) aphysicalchemical agent to emulsify the insoluble sub.- stances in acolloidal form thereby rendering the colloidal particles to be freelydispersed and substantially non-retainable in the web of the recoveredstock.

In performing our process the newsprint is shredded and then mixed witha solution of alkaline agent substantially of the following composition:

Per cent Alkali extract of coniferous bark 0.25 Detergent (such assodium silicate, sodium carbonate, trisodium phosphate, etc.) 0.5Caustic soda 0.1

A method for obtaining bark extract suitable for our purposes is tosteam the coniferous bark for about 2 hours at a pressure of about 6atmos pheres whereupon the bark is ground to a powder by any suitablemeans. About 100 grams of ground bark are extracted with about 400 cc.of about 10 per cent caustic soda, and while a continuous system ofextraction is preferred, intermittent extraction methods are also withinthe contemplation of this invention. If continuous extraction is used,the alkali solution may be continuously allowed to flow by means ofgravity through a tall column containing the bark until substantiallyall the extractives have been extracted. The extracted bark is thenwashed with water and the solution plus wash waters is brought up to atotal volume of 8,000 cc.

This extraction procedure can be done hot or cold, but hot solutions arepreferred because greater amounts of emulsificants are extractedthereby.

The degree of dilution of the 400 cc. of 10 per cent caustic sodaextract varies with the species of conifer used in the extractionprocess. The dilution to 8,000 cc. being a good average concentrationfor effective deinking purposes, but a dilution of the 400 cc. ofextract from 100 grams of pine bark to 12,000 cc. is feasible.Furthermore the 400 cc. alkaline extract from spruce may be effectivelydiluted to 24,000 cc. thereby producing an effective deinkingconcentration, while 400 cc. of alkaline extract of fir may be dilutedto 35,000 cc. and yield an equally effective emulsificant.

The newsprint to be pulped is added to the diluted emulsificant.mentioned above to give a pulp concentration of from 5 to '7 per cent;thus about 400 to 500 grams of newspaper are added to 8,000 cc. ofemulsificant. This mixture of newspaper and emulsificant is thendisintegrated by any suitable means as for example a beater, hydrapulperor the like. The pulp is then dewatered to a concentration of about percent in a screw press, vacuum filter or other means and then washed freefrom carbon particles. The washed pulp has substantially the whitenessof the original newspaper pulp. If there be a slight yellowing due tocaustic soda, it may be corrected by the addition of a small amount ofsodium acid sulfite solution.

The waste liquor obtained after the extraction process may beregenerated for re-use by first diluting about 300 00., with fresh 10per cent caustic soda to a total volume of 400 cc. One hundred grams ofsteamed, ground coniferous bark is then extracted with this regeneratedsolution and the extract with its wash waters are diluted as previouslynoted to about 8,000 cc. In this regeneration process the carbon blackparticles are retained by the ground bark. When using the regeneratedprocess, the average fresh bark consumption amounts to about 6.2 percent of the weight of newsprint deinkedand the caustic soda consumptionamounts to about 3.25 per cent of the weight of the newsprint deinked.Repeated use of the regenerated solution tends to concentrate theconiferous emulsificants, so that the amount of fresh bark required maybe substantially less than the 6.2 per cent mentioned above. The barkextract may be obtained from wood pulp operations wherein coniferouslogs are steamed in order to assist in the debarking of the logs,yielding a waste bark ideally suitable for deinking purposes. Steamingof coniferous bark at pressures from substantially zero to 10atmospheres for periods of 1 to 4 hours is practical but bark steamed atabout 6 atmospheres and for about 2 hours is preferred.

If non-steamed bark is used, the caustic extract has a marked reddishbrown color which is imparted to the recovered newsprint. Steamed barkon the other hand gives a substantially colorless extract of greaterefficiency and stability. Furthermore the steaming process facilitatesthe rapid extraction with the 10 per cent caustic soda since thesteaming makes the ground bark more porous.

Bark as normally obtained in the air dry condition is used. Moreover,the steaming and extraction procedures may be conducted in the sameextraction apparatus. Furthermore, while we prefer caustic soda as oursource of alkalinity for the extraction process and admix therewith suchalkaline detergents as sodium silicate, trisodium phosphate, sodiumcarbonate, etc., we have found that use of said alkaline detergents,without addition of excess caustic soda, but admixed with coniferousbark extract will also remove carbon particles, though not quite aseffectively a when added caustic is present.

Thus bark extracted with, for example, a solution of trisodium phosphateyields a solution effective in the removal of carbon particles fromnewsprint.

This invention has been illustrated by means 51 of embodiments thereofbut it is to be understood that the scope of the invention is notlimited to the illustrative embodiments herein presented.

We claim: I 1. The process of de-inking newspaper slurry comprisingemulsifying the ink particles in said slurry with an emulsifyin solutionconsisting 01' a caustic soda extract of steamed resinous coniferousbark.

2. The process of de-inking newspaper slurry comprising emulsifying theink particles in said slurry with an emulsifying solution consisting ofa caustic soda extract of steamed resinous coniferous bark, separatingsaid emulsifying solution from said slurry, and regenerating saidemulsifying solution by passing it through a column of steamedcomminuted resinous coniferous bark.

3. The process of deinking newspaper consisting essentially of shreddingthe newspaper, emulsifying the ink binder of said newspaper with an0.25% alkaline aqueous extract of steamed resinous coniferous bark,beating the shredded particles to separate the wood fibers and also theemulsified ink particles, dewatering the disintegrated stock to removethe emulsified solution containing ink particles, and washing saiddewatered stock to float away any residual ink particles. I

JEAN ERNEST ZiiNDEL. ROBERT S. ARIES.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 228,955 Terne June 15, 1830 354,855 Friede Dec. 21, 18861,281,670 Schmid Oct. 15, 1918 1,572,478 Hammond Feb. 9, 1926 1,601,193Welsh Sept. 28, 1926 1,925,372 Darling Sept. 5, 1933 1,933,227 Snyder eta1. Oct. 31, 1933 1,933,228 Snyder et a1. Oct. 31, 1938 2,018,938 WellsOct. 29, 1935 2,116,511 Earle May 10, 1938 2,220,950 Bird Nov. 12, 19402,346,909 Dahl-Rode Apr. 18, 1944 2,403,143 Tutt July 2, 1946 2,505,818Williams May 2, 1950 OTHER REFERENCES Printing Inks, by Ellis, publishedby Reinhold, New York (1940) pages 480, 481.

Whittaker and Bates: Chemical Utilization of Southern Pine Waste, TheJournal of Industrial and Engineering Chemistry, vol. 6, No. 4, April1914, pp. 289298 (of which pp. 297-298 are relied upon).

1. THE PROCES OF DE-INKING NEWSPAPER SLURRY COMPRISING EMULSIFYING THEINK PARTICLES IN SAID SLURRY WITH AN EMULSIFYING SOLUTION CONSISTING OFA CAUSTIC SODA EXTRACT OF STEAMED RESINOUS CONIFEROUS BARK.